Induction heating



p 1957 H. LINDSTROM 2,805,309

INDUCTION HEATING Filed Sept. 20, 1955 INVENIQR. Hugo Lmdsfrom United States Patent INDUCTHON HEATING Hugo Lindstriim, Vasteras, Sweden, assignor to Ailmannn Sveusha Elektriska Aktiehoiaget, Vasteras, Sweden, a corporation of Sweden Appiication September 20, 1955, Serial No. 535,329 Claims priority, application Sweden September 21, 195% 3 Claims, (Cl. 21919.51)

A known device for local heating of articles with high frequency current disclosed in the U. S. A. Patent No. 2,599,086, consists of a transformer having a ringshaped iron core, a toroidal primary winding and a secondary winding, which is formed by a slit metal casing in the shape of a substantially circular box having in its opposite plane sides central openings of different diameters. Fixed on the edges of said openings of the casing are concentric metal tubes protruding axially from the casing and supporting on their inner wall surfaces the parallel legs of an U-shaped, hollow, water-cooled heating element. On the upper side of the casing there are arranged the connections for the cooling fluid and the supply leads for the primary winding. The cooling fluid enters the one leg of the heating element, passes through said element and the hollow primary winding and leaves the device through rubber hoses. Such a device works rather satisfactorily as concerns the cooling, but it is simple to improve the cooling effect and to simplify the manufacture and to render it cheaper when a construction is used according to the present invention.

The principal feature of the present invention is that the casing consists of a hollow metallic ring having a circular slit tightened by insulating material, that the end of the one leg of the U-shaped heating element is fixed to thechamber formed by the inner wall of the casing, and the end of the other leg is fixed to an excentric located opening in the casing, that both the transformer core and the primary winding surrounding it are embedded in a cooling fluid, preferably water, and that the heating element and the casing provide series-connected passageways for the cooling fluid.

Other features of the invention will become apparent from the following description in connection with the accompanying drawings but the invention is not limited to the exact details of the construction shown and described only by way of example.

eferring to the drawings:

Fig. 1 shows a section through the heating device taken along the lines AA in Fig. 3 and partly through the heating element taken along the lines BB in Fig. 2.

Fig. 2 shows the heating device viewed from below.

Fig. 3 shows the heating device viewed from above.

Like parts throughout the various figures are designated by like reference numerals.

The ring core 1 supports the toroidal primary winding 2 which is enclosed in a casing 3 in the shape of a hollow metallic ring, which is slit at 3' and tightened by insulating material thus forming the secondary winding. The inner tubular part or wall 4 of the casing has its upper end fixed to the plane side 5 of the casing, while its lower end, electrically insulated from the part 6 is connected with the end of the one leg of the U-shaped heating element. The end of the other leg is fixed on an excentrically located opening of the casing. The cooling fluid enters through a hose 8 of rubber or the like the chamber formed by the inner wall 4 passes 2,805,309 Patented Sept. 3, 1957 through the hollow heating element 7, the casing along the winding 2, and leaves the device through two hoses 9 attached to the upper side of the casing and surrounding the electric connection leads 10 to and from the primary winding. In the case that the cooling fluid is electrically conductive the iron core, the primary winding and the supply leads have to be insulated from the cooling fluid. The individual sheets of the core, then are suitably coated with a varnish and pressed together, and also the assembly is provided with an insulating coating. The primary winding is suitably insulated by rubber or synthetic resin. Due to the fact that the primary winding is cooled on both sides, and also the connection leads by the cooling fluid traversing the hoses, the cooling eflect is considerably improved. The connection leads and the hoses are protected against mechanical stresses by collars 11. The casing may be manufactured by soldering or welding the tubes 3 and 4 to the plane sides 5 and 6, respectively. It is also possible that the one leg of the heating element is extended through the height of the casing, so that it forms the inner wall 4 thereof. The manufacturing of the device is greatly simplified by the construction according to the invention.

In order to concentrate the heat to a certain spot of the work piece the heating element may be embedded within an iron core 12 (indicated by dash lines). The active portion of the heating element may be made exchangeable for fitting to various forms of the work piece to be heat-treated.

What I claim is:

1. A high frequency induction heating device for 10- cally heating a work piece, comprising a toroidal primary winding, a ring-shaped iron core surrounded by said winding, a secondary winding consisting of a casing in the shape of a hollow metallic ring having a circular slit tightened by insulation material and enclosing the primary winding, a hollow substantially U-shaped heating element having the end of one leg attached to a central chamber confined by the inner wall of the casing, and the end of the other leg attached to an excentrically lo cated opening in one plane side of the casing, and hoses for the cooling fluid attached to the said hollow casing and to the said central chamber, respectively, the casing and the hollow heating elements constituting cooling fluid conducting elements so arranged that the cooling fluid entering through a hose attached to the said central chamber and passes through the casing along said primary winding and leaves the casing through said hoses attached to the casing.

2. A high frequency induction heating device according to claim 1, in which the primary winding has its connection leads enclosed in hoses traversed by cooling fluid.

3. The method of cooling a high frequency induction heating device as described and illustrated, in which the cooling fluid is caused to enter the central chamber confined by the inner wall of the casing, to pass through the heating conductor, through the space between the casing and the primary winding, and to leave the device through hoses containing electrical connection leads for the primary winding.

References Cited in the file of this patent UNITED STATES PATENTS 2,407,562 Lofgren Sept. 10, 1946 2,513,242 Inman June 27, 1950 2,599,086 Beckius et al. June 3, 1952 2,644,881 Schorg July 7, 1953 FOREIGN PATENTS 635,421 Great Britain Apr. 12, 1950 

